This simply how to implement the module of permutations in python.

>>> from itertools import permutations
>>>
>>> perms = [''.join(p)+"@gmail.com" for p in permutations('abc', 3)]
>>> for email in perms:
...     print(email)
...
abc@gmail.com
acb@gmail.com
bac@gmail.com
bca@gmail.com
cab@gmail.com
cba@gmail.com
>>>